Effect of wear-debris particles on RAW 264.7 cells

Wear-debris particles from ultrahigh molecular weight polyethylene (UHMWPE) and metals has been implicated in periprosthetic osteolysis and cellular response to them depend on their size and dose. Response to larger particles has been previously studied, but there are no specific studies examining biological response to simultaneous administration of both UHMWPE and Ti particles less than 0.2¿m in size. Our lab has developed a standardized and reproducible technique to isolate, characterize and fractionate both particles into 3 distinct size ranges [1.0-10.0¿m (micron), 0.2-1.0¿m (submicron) and 0.01-0.2¿m (nano)] and furthermore minimize clumping, which facilitated disaggregation and isolation of individual particles. RAW 264.7 cells were treated for 24h, 48h and 72h with various doses and sizes of both particulates simultaneously. Cell membrane damage was measured by quantifying lactate dehydrogenase (LDH) release. The cells elicited a dose and size dependent response to the nano-particulates at the highest dose. At 72h there was a significant increase in LDH released by cells treated with the nanoparticles as compared to untreated controls as well as to larger particles. To mimic in vivo conditions, further studies are being conducted and will involve administration of dual wear particulates that will help understand cellular response to wear particulates.